Person: Fernández Castillo, Jesús
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First Name
Jesús
Last Name
Fernández Castillo
Affiliation
Universidad Complutense de Madrid
Faculty / Institute
Ciencias Químicas
Department
Química Física
Area
Química Física
Identifiers
8 results
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Item Structural, magnetic and luminescent characteristics of Pr3+-doped ZrO2 powders synthesized by a sol–gel method(Journal of Physics D: Applied physics, 2009) Isasi Marín, Josefa; Pérez Estébanez, Marta; Díaz-Guerra Viejo, Carlos; Fernández Castillo, Jesús; Correcher, Virgilio; Cuervo Rodríguez, María RocíoThe structural, magnetic and luminescence properties of praseodymium-doped zirconia powders of compositions Pr0.03Zr0.97O2 and Pr0.05Zr0.95O2 synthesized by a sol–gel process have been investigated. X-ray diffraction patterns indicate that these materials crystallize in a tetragonal fluorite-type structure. Scanning electron microscopy shows that the powders exhibit an agglomerated microcrystalline structure and the grain size may be in the order of 5–20μm. The study of the magnetic properties of these doped metal oxides indicates a Curie–Weiss behaviour in the temperature range (100–300)K that allow us to estimate an effective magnetic moment of 3.51μB, which indicates the presence of Pr3+ in the grown samples. Cathodoluminescence spectra recorded at temperatures between 85 and 295K show emission peaks that can be attributed to transitions between different states within the 4f2 configuration of Pr3+ ions incorporated in the zirconia crystal lattice. Thermoluminescence measured at temperatures ranging from 373 to 773K and at 550 nm wavelength show an intense and broad peak around 653K for the Pr-doped zirconia which is not observed in the undoped material.Item Geometric form of volcanoes with a limited based(XXI Congreso de Ecuaciones Diferenciales y Aplicaciones XI Congreso de Matematica Aplicada, 2009) Arjona, Alicia; Díaz Díaz, Jesús Ildefonso; Fernández Castillo, JesúsMany volcanic constructs have geometric different shapes depending on different phenomena as parasitic cones, erosion or coral growth. In Lacey, Ockendon and Turcotte [11] the authors proposed a nonlinear model proving that the shape of volcanoes is determined by the hydraulic resistance to the flow of magma, from a line source, through the porous edifice. This model was later extended in Angevine, Turcotte and Ockendon [2] to include the shape of aseismic, submarine ridges. In this communication we propose a modification of the above mentioned models in order to simulate the more realistic case of volcanoes with a limited base.Item Geodetic and Structural Research in La Palma, Canary Islands, Spain: 1992-2007 Results(Pure and Applied Geophysics, 2008) Prieto, J. F.; Gónzalez, P. J.; Seco, A.; Rodríguez Velasco, Gema; Tunini, L.; Perlock, P.A.; Arjona, Alicia; Aparicio, A.; Camacho, A. G.; Rundle, J.B.; Tiampo, K.F.; Pallero, J. L. G.; Pospiech, S.; Fernández Castillo, JesúsWe review the results of the geodetic and structural studies carried out on La Palma Island using geodetic and geophysical data during the period 1992-2007. InSAR and GPS observation techniques were applied to study the existence of deformation on the island and gravity observations were carried out for structural studies. Gravity data were inverted using a nonlinear three-dimensional gravity inversion approach to obtain the geometry of the anomalous bodies constructed in a random growth process with respect to an exponentially stratified background. The main structural feature is a large central body (under the Caldera de Taburiente) with high density, which was interpreted as the Pliocene-age uplifted seamount and a relatively dense intrusive plutonic complex/magma body. The Cumbre Vieja series is characterized by elongated minima distributed according to the rift structure. InSAR results show a clear subsidence located on the Teneguia volcano, where the last eruption took place in 1971. A thermal source is the most probable origin for this deformation. A GPS network composed of 26 stations covering the total island surface was set up. Vertical displacements determined comparing the GPS coordinates obtained in 2007 with coordinates determined in 1994 are consistent with the InSAR results obtained in the southern part of the island. This is not the case for the northern part. From the comparison of 2006 and 2007 coordinates it is clear that more time is needed to obtain significant displacements, but observed trends are also consistent with InSAR results. All the observed significant displacements are in stations located outside of the large high-density central body.Item Detection of displacements on Tenerife Island, Canaries, using radar interferometry(Geophysical Journal International, 2005) Fernández Castillo, Jesús; Romero, Rosana; Carrasco, Daniel; Tiampo, K. F.; Rodríguez Velasco, Gema; Aparicio, A.; Araña, V.; Gónzalez Matesanz, F. J.Tenerife is one of the most well monitored islands of the Canaries, but the surveillance generally is centred on Las Canadas Caldera, where the Teide volcano is located. In the last 180 000 yr, the eruptions on Tenerife Island have never occurred in the same volcanic structure, except for the Teide and Pico Viejo central volcanic system, so that a complete monitoring network would have to cover the whole island. As a result, Synthetic Aperture Radar Interferometry (InSAR) is being used on Tenerife, because this space technique can provide a displacement map of the surface of the earth with centimetre precision. This paper presents the results obtained on Tenerife Island using 18 SAR images acquired by the ERS-1 and ERS-2 satellites during the period 1992-2000. Two important results have been obtained: no deformation on Las Canadas Caldera, coinciding with results obtained using terrestrial techniques, and two subsidence episodes outside monitoring areas in the NW of the island, in the region of the last historic eruptions. These results show that InSAR is a useful technique for monitoring the entire island, thus allowing us to discover deformations in areas that are not routinely or easily monitored. This technique has been used in combination with Global Positioning System (GPS) observation of a global network on the island to define a new geodetic monitoring system. The possible causes of the deformations observed have been studied in an endeavour to discern if they might be of natural origin, in particular linked to a reactivation of prior volcanic activity. Examination of the geophysical observations on the island, human activities underway and the results of the modelling seem to indicate that at least part of the deformations may be caused by changes in the groundwater level and therefore are not linked to a volcanic reactivation. This result is important because it implies that, if geodetic volcano monitoring is to be performed on the island, the system used must be capable of discerning between various possible origins of the deformation by analysing their patterns and ancillary information from other sources. In this regard, InSAR is a basic tool on account of its unpaired wide area coverage and spatial density.Item GPS monitoring in the N-W part of the volcanic island of Tenerife, Canaries, Spain: Strategy and results(Pure and Applied Geophysics, 2004) Fernández Castillo, Jesús; Gónzalez Matesanz, F. J.; Prieto, J. F.; Rodríguez Velasco, Gema; Staller, A.; Alonso Medina, A.; Charco Romero, MaríaThis paper describes design, observation methodology, results and interpretation of the GPS surveys conducted in the areas of the N-W of Tenerife where deformation was detected using InSAR. To avoid undesirable antenna positioning errors in the stations built using nails, we designed and used calibrated, fixed-length metal poles, allowing us to guarantee that the GPS antenna was stationed with a height repeatability of the order of 1 mm and of less than 3 millimeters on the horizontal plane. The results demonstrate that this system is ideal for field observation, especially to detect small displacements that might be masked by accidental errors in height measurements or centering when observed with a tripod. When observations were processed, we found that using different antenna models in the same session sometimes causes errors that can lead to rather inaccurate results. We also found that it is advisable to observe one or two stations in all the sessions. The results have reconfirmed the displacement in the Chio deformation zone for the period 1995-2000 and indicate a vertical rebound from 2000 to 2002. They also confirm that the subsidence detected by InSAR to the south of the Garachico village has continued since 2000, although the magnitude of the vertical deformation has increased from around 1 cm to more than 3 cm a year. Detected displacements could be due to groundwater level variation throughout the island. A first attempt of modelling has been made using a simple model. The results indicate that the observed deformation and the groundwater level variation are related in some way. The obtained results are very important because they might affect the design of the geodetic monitoring of volcanic reactivation on the island, which will only be actually useful if it is capable of distinguishing between displacements that might be linked to volcanic activity and those produced by other causes. Even though the study was limited to a given area of Tenerife, in the Canary Islands, some conclusions apply to, and are of general interest in similar geodynamic studies.Item New geodetic monitoring system in the volcanic island of Tenerife, Canaries, Spain. Combination of InSAR and GPS techniques(Journal of volcanology and geothermal research, 2003) Fernández Castillo, Jesús; Yu, T. T.; Rodríguez Velasco, Gema; González Matesanz, J.; Romero, R.; Rodríguez, G.; Quirós, R.; Dalda, A.; Aparicio, A.; Blanco, M. J.Even though volcanic activity in Tenerife is characterized by the fact that eruptions do not normally occur more than once in the same volcanic edifice, geodetic monitoring has mainly focused on the Las Canadas Caldera, where a geodetic micronetwork and a levelling profile are located. A sensitivity test of this geodetic network showed a clear need to extend it to cover the full island for volcano monitoring purposes. This conclusion, together with the detection of two unexpected movements on the island using InSAR that were beyond the scope of the traditional geodetic network, prompted the authors to design and observe a GPS network covering the whole of Tenerife. The network was monitored in August 2000. The results obtained were accurate to 1 cm, and confirm the deformation in the Pinar de Chio zone, but are not definitive enough to confirm the displacements detected to the south of the village of Garachico. Furthermore, new cases of possible subsidence have been detected in areas where InSAR could not be used to measure deformation due to low coherence. Future observations will be necessary for further validation and to study the time evolution of the displacements, and supplementary research must be conducted to determine the possible causes, in particular if they are connected with the water pumping operations performed on the island. One important result is that a new geodetic monitoring system based on two complementary techniques, InSAR and GPS, has been set up on Tenerife island. This is the first time that the whole surface of any of the volcanic Canary Islands has been covered with a single network. This research has displayed the need for further similar studies in the Canary Islands, at least on the islands which pose a greater risk of volcanic reactivation.Item Sensitivity of the MM5 mesoscale model to physical parameterizations for regional climate studies: Annual cycle(Journal of geophysical research-atmospheres, 2007) Fernández Castillo, Jesús; Montávez, J. P.; Sáenz, J.; González Rouco, Jesús Fidel; Zorita, E.We present an analysis of the sensitivity to different physical parameterizations of a high-resolution simulation of the MM5 mesoscale model over the Iberian Peninsula. Several (16) 5-year runs of the MM5 model with varying parameterizations of microphysics, cumulus, planetary boundary layer and longwave radiation have been carried out. The results have been extensively compared with observational precipitation and surface temperature data. The parameterization uncertainty has also been compared with that related to the boundary conditions and the varying observational data sets. The annual cycles of precipitation and surface temperature are well reproduced. The summer season presents the largest deviations, with a 5 K cold bias in the southeast and noticeable precipitation errors over mountain areas. The cold bias seems to be related to the surface, probably because of the excessive moisture availability of the five-layer soil scheme used. No parameterization combination was found to perform best in simulating both precipitation and surface temperature in every season and subregion. The Kain-Fritsch cumulus scheme was found to produce unrealistically high summer precipitation. The longwave radiation parameterizations tested were found to have little impact on our target variables. Other factors, such as the choice of boundary conditions, have an impact on the results as large as the selection of parameterizations. The range of variability in the MM5 physics ensemble is of the same order of magnitude as the observational uncertainty, except in summer, when it is larger and probably related to the inaccuracy of the model to reproduce the summer precipitation over the area.Item Time Evolution of Deformation Using Time Series of Differential Interferograms: Application to La Palma Island (Canary Islands)(Pure and Applied Geophysics, 2008) Perlock, A. P.; Gónzalez, P. J.; Tiampo, K. F.; Rodríguez Velasco, Gema; Samsonov, S.; Fernández Castillo, JesúsDifferential interferometry is a very powerful tool for detecting changes in the Earth's crust where coherence conditions are good, but is difficult to employ in some volcanic areas due to dense vegetation. We apply two differential InSAR methods using the time series associated with the interferograms to perform a phase analysis on a data set for La Palma island (Canary Islands) from the ERS-1 and ERS-2 European Space Agency (ESA) satellites for the time period 1992 to 2000. Both methods involve choosing a master image from the database and creating a series of interferograms with respect to this image. The "Coherent Pixel Time Series" (CPTS) technique chooses pixels with good average coherence, aligns the unwrapped interferograms with a stable area and then performs an inversion to calculate the linear velocity to quantify the deformation. The Coherent Target Modeling (CTM) method calculates the temporal coherence of each pixel to identify stable targets and then determines the best velocity for each pixel by using a linear fit that maximizes the temporal coherence. Using these two methods we have been able to detect deformation on La Palma Island that has been previously undetectable by conventional InSAR methods. There is a roughly circular region on the Southern part of the island that is actively deforming at -4 to -8 mm/yr. This region is located near the Teneguia valcano, the host of the last known eruption on La Palma in 1971. A thorough investigation of the possible sources for this deformation revealed that it was most likely created by a subsurface thermal source.